Hi,
As far as Quickbooks POS is concerned, that is a web / mobile and desktop based application and is having customer relationships, manage inventory and automate the overall banking process. Thus, this is not a small job and having so many phases, modules barcode scanning, credit card processing, price lookup, receipt notes, refunds, discounts, exchanges etc..
This is a big data project and I have quoted accordingly because we have POS development experience as well as QB integration skills.
Let me know when we may discuss.
Regards,
Mit-